In vertical cave exploration today, the fixed rope is used for basically two purposes: lowering oneself down from the tie-off point to the bottom, and the reverse, returning to the top from the bottom. This article is concerned with the former: the equipment, theory, and technique of descending a rope safely.
Descending, commonly known as rappelling or abseiling (European), is today generally accomplished with some type of mechanical friction device. Simple physics tells us that an object (the caver) at a higher elevation possesses more potential energy than does an object at a lower elevation, and that energy is neither lost nor created, but simply changes form. When a caver descends a drop he begins with more potential energy than he ends up with after allowing gravity to work on his weight. This energy is not lost, but is translated through friction into heat and stored mechanical energy. It is the careful, controlled conversion of this energy with which we are concerned.
All types of rappelling require an instrument, whether it be the caver’s body or some manufactured device, which converts potential energy through friction into heat. Anyone who has used the body as a friction device knows about heat production, and possibly about rope burns.
- 1 Classic Body Rappel
- 2 Rappel Devices
- 3 Rappelling Techniques
- 4 Instruction & Practice
Classic Body Rappel
Although the body rappel is extremely uncomfortable, it still has its emergency uses, and may at times be used in conjunction with mechanical rappelling devices. To achieve the correct rope configuration, the caver faces the rope’s anchor with his back to the drop. The rope passes through his legs, around the right hip, and then goes across his chest from the lower right to the left shoulder. From here the rope passes diagonally to the right hand, which is held at approximately waist level. The caver’s left hand is placed on the rope in front of him for balance. By allowing rope to slide through the right hand, the caver thereby regulates his speed of descent. (The pressure will tend to make you assume a fetal position. Do not allow yourself to get in this position, as it is nearly impossible to straighten back up.) The caver needs nothing more than a rope to accomplish this descent, which makes it attractive for emergency use. However, this type of rappel is quite uncomfortable, and it is therefore normally used only for very, very short drops or in emergencies.
Today there are many kinds of rappel devices (also referred to as descenders) available. We will go over the simpler ones first, moving to the more complicated ones later. All of the rappel devices described here are attached to the caver’s seat sling or harness by means of a locking carabiner.
This type of friction device is quite simple, using only one carabiner. The rope is wrapped two or three times around the side of the carabiner opposite the gate. The carabiner should be of the locking type. Be sure the rope does not rub against the sling, as the nylon rope will melt through the sling very quickly. Again, one hand is held in front for balance, and the other, held low, regulates the amount and speed of the rope to be passed through the carabiner. If speed increases, making it too difficult to keep a slow pace, increase friction by moving your braking hand to position the rope across some portion of your body. This method can be employed with any mechanical rappelling device.
Although the carabiner wrap method is used by many military personnel, it is not recommended as a standard means of rappelling. Not only is it not as safe as other methods, but it weakens that particular carabiner through heat and abrasion, and it weakens the rope.
Brake bars are simply round aluminium rods approximately 4 inches long with a hole drilled through one side to fit a carabiner. The other end of the brake bar has a slot machined across it to allow it to lock into the other side of the carabiner. The rope is placed through the carabiner, up over the brake bar, and back through the carabiner. Because of the machined slot in the brake bar, it can hinge up so you can simply put the bight in the rope, push it through the carabiner, and snap the brake bar back in place. This is much simpler than threading the rope through, starting at one end. Be sure the brake bar is situated correctly: If the rope is inserted backward, the brake bar will snap open as soon as any force is put on it. The carabiner brake bar setup is clipped into the caver’s harness via a locking carabiner. If locking carabiners are not available, as a second choice use two non-locking carabiners with gates reversed.
A caver may use, as needed, any number of these carabiner brake bar setups. They should be connected with continuous links or looking carabiners. Generally one brake bar is used with double ropes. Double brake bar setups should usually be used with a single rope.
The figure 8 rappelling device is becoming quite popular for short to intermediate drops. To rig the figure 8, a bight is taken in the rope and passed through the large ring on the 8 ; the smaller ring is then stuck through the bight. The small ring is clipped into the harness again, and the caver uses one hand for balance and one for control. The figure 8 is exceptionally safe, as it is nearly impossible to hook up incorrectly.
The longhorn 8, manufactured by Mountain Safety Research, is essentially an extension of the idea of the figure 8. It has curved catches on it so that the rappeller can wrap the rope around these hooked catches to slow or stop the descent completely. (Again, remember that nylon on nylon melts.) The main advantage of the longhorn 8 is that it does not have to be unsnapped from your seat sling to hook in. All of the foregoing rappel devices are static; that is, they produce essentially uniform friction, and do not allow the device itself to change in such a way as to produce more or less friction. Some increased friction can be obtained by using the controlling hand to pull harder on the rope to make the rope turns tighter, but this does not involve a mechanical change in the rappelling device.
For serious vertical cave exploration where substantially long drops are encountered, such as those of 150 feet or more, it is important that the caver use some sort of variable friction rappel device. In use on a long drop, the rope arrangement through the device at the top of the pitch is arranged to create less internal friction because the mere weight of the standing rope hanging below the friction device may be quite significant, causing increased friction. Indeed, this weight may be sufficient to lock up a rappel device completely and prevent any rappel, unless the rope is forcefully fed through the device, a very tiring and inefficient method. As the caver rappels down, the amount of rope hanging below is continuously reduced, hence the weight becomes less. Because of lessened weight and hence lessened friction, speed will increase unless the mechanical descending device is adjusted to create more internal friction. For these reasons, as well as the fact that they dissipate the heat more effectively as a result of their larger sizes, most serious vertical cavers use one of the rappel devices described below.
This is more properly known as the rappel rack and was designed by John Cole in 1966. It is essentially a U-shaped piece of round steel bar upon which a series of brake bars is added. Cavers usually use a series of six bars. These bars are positioned so that they swing open in opposite directions alternately, and the rope goes over one and under the next. The bars are also able to slide up or down. Holding the lower brake bars in his hand, the caver is able to push them up. As the bars move upward the rope is forced to take tighter turns, thus creating more friction and slowing the descent.
By spreading the bars farther apart, the friction is reduced and speed is increased. Another method of regulating friction, hence speed, is by beginning the descent with four or five bars when the rope below weighs enough to create increased friction. As the caver descends and the friction produced by the rope decreases, he may flip in additional brake bars to produce additional friction. By pulling the free end of the rope up and over the end of the rack, the caver can lock the rack up, arrest his descent, and free both hands. The first three bars of the rack should be slightly filed in the centre to produce small grooves in which the rope should track. Never allow the rope to track off centre, as this not only produces non-uniform stresses, but also may damage the rack itself through abrasion and heat. It has been reported that if the rope tracks off centre, it may become very difficult to shift the bars to adjust friction. The first three bars will wear more than the others, and once worn should be switched with the bottom three at some point so as to get uniform wear. When the bars have worn down to the point where they do not cause the rope to take tight enough turns, they should be replaced.
Occasionally on long drops the weight of the hanging rope will cause the first two bars to pinch, creating much friction and heat, which is not dissipated efficiently. Not only is heat damaging to the ropes, but handling the brake bars in this situation is next to impossible, even with gloves. Many cavers are modifying their racks to suit long drops better by replacing the top two 18-millimeter bars with 25millimeter machined square aluminium bars, or by replacing the top two independent bars with two pairs. This provides much more efficient heat dissipation because of increased mass. To avoid the pinching effect of the top two bars, one can place 20-millimeter-long brass tubing spacers between them.
The standard rack is U-shaped at one end and open at the other with an eye for carabiner attachment. The Opening allows the rope to be moved in or out to add or subtract brake bars. Be sure when selecting a rack that the eye is of secure construction. Even if the rack itself is strong enough, some tend to begin bending with loads of 250 kilograms and fail with 500 to 1,000 kilograms by unwrapping at the eye.
The rope should never run over the rack end, as this will weaken it. The rope should always run over a bar on the end.
A modification of the rack to form a super rack began to gain popularity in 1973. The super rack is again a U design; however, the point of attachment is at the bottom of the U, and the two free ends are threaded and nuts are screwed in place to prevent the bars from coming off. Generally there are five 25-millimeter square aluminium brake bars present, and all are always used. The bars are notched to position the rope and avoid the square corners. Spacers are generally positioned between the first two bars to prevent pinching. Because of the increased mass of aluminium in the bars, heat dissipation is much improved.
The super rack works well on long drops where hanging rope weight is encountered; however, near the bottom or on short drops when rope weight is slight, some cavers report that because of the decreased friction, speed is often much harder to regulate, and the caver may descend too rapidly.
The whaletail was originally invented in the United States, but was modified to its present form in Australia. The whaletail is a piece of aluminium with a series of slots machined into it so friction can be varied according to the number of slots through which the rope is wound.
Rappelling is one of the easiest, most exciting areas in vertical cave exploration. It is also a very safe aspect of vertical caving if the caver uses good judgement. Although a substantial percentage of caving accidents happens during rappelling, most of such accidents can be divided into two general categories. The first involves novices who do not have the proper equipment and have had no instruction in the proper techniques. The second involves experienced individuals who through overconfidence fail to follow safety procedures.
Initiating A Rappell
When the bottom of a pit cannot be seen or there is any possibility that the rope will not reach the bottom of the drop, it is a very wise procedure to tie a fig8 knot in the end of the rope, forming a small loop. Many a caver has rappelled off the end of the rope without such a precaution.
To initiate a rappel the caver first faces the properly anchored rope with his back to the drop, which should be well back from the preparing caver. He then takes the rope and properly positions it through the descender he is using. The descender should be attached to his seat sling by means of a locking carabiner. Once the rope is threaded through the descending device, make sure the locking carabiner is locked. At this point the caver should take up all slack in the rope between the anchor and himself by feeding the rope through the descending device.
Now the caver needs to arrange the standing rope through his braking hand into the desired configuration about the body. (The braking hand is generally the individual’s favoured hand.) Many cavers favour having the rope leave the descender to travel around their side through the braking hand in such a way that substantial friction can be induced by pulling the rope around the hip toward the back. The body thereby provides increased friction. Normally simply increasing or decreasing the hand pressure on the rope will be sufficient to regulate speed. Some cavers prefer to run the rope through the legs with the braking hand directly behind the buttocks. Still others prefer the rope to pass through the legs and around the hip and thigh to the braking hand in front.
Some prefer to run it around the back to the Opposite hip. The body-rope configuration decided upon will stem from personal preference, the type of equipment used, and the type and length of the drop. The non-braking hand is generally positioned on the rope above the descender for balance. This hand is not used for speed regulation or control, but simply for balancing. Those individuals using racks will find that they often prefer to leave their braking hand in front, below the rack. The left hand is used to cradle the brake bars, moving them up or down. Because of the rack’s length, balance is not sacrificed. Make sure the descending rope does not rub against the seat sling, as it will melt through it.
The caver now begins to back toward the edge, double-and triple-checking his descender for proper rope positioning and to be sure the descender is securely attached to his seat sling via a locked carabiner. It is a good idea to check occasionally, on the way down as well.
With a brake bar setup, if the rope gets slack in it, as it sometimes does, bars have been known to slip open. Also, with brake bars, be absolutely positive about position. Many individuals have died because the rope was threaded backward in relation to the brake bars (suicide rigs) ; a minute force was put on the system, the bars popped, and the rope fell free.
The caver plants his feet at least shoulder width apart, and placing his weight against the anchor, backs to the edge. Slowly, one foot at a time, he walks over the edge, allowing the rope to feed slowly through his braking hand. Often times there will be so much friction the caver will have to feed the rope through the descender until he is on his way. However, never let go of the rope with your braking hand.
It is the first few steps over the edge that are by far the hardest. In reality it is quite simple-you simply walk down backwards, regulating speed with your braking hand. The initial phases of walking over the edge become a bit more intense when the edge is an overhanging lip. In the case of an overhang, simply lower your buttocks down to below the level of your feet, gently push off springing your knees, un-plant your feet, and you will swing in and under to where you will be hanging free. When free, you simply sit in your seat sling as if in a chair and lower yourself down.
Be careful when going over a very abrupt edge with a rack. When you come down you do not want your rack to end up halfway over the edge and become deformed and bent.
You want your rappel to be a slow and controlled one, Descent speed should not exceed about 20 yards per minute, and less is recommended. Do not try to impress your friends by bouncing out in long leaps and bounds as demonstrated on television. This and abrupt stops put great stresses on the system-anywhere from 94 to 169 percent.
While enroute, if you find you need additional braking that exceeds what you can accomplish with your braking hand, a very quick and effective way to increase friction and hence braking is to use your leg and/ or foot. Swing your leg back, hooking your foot around the rope, thereby wrapping it around the leg. If this is still not sufficient, hook the rope again with the other foot.
It is important to use proper call signals throughout the descent.
When rappelling, the caver must secure all loose clothing, hair, and electric wires out of the descender’s area. Anything loose tends to be pulled into the descender where it then jams. If this should occur, the first and most important step is to stop and evaluate the situation.
In the case of caught hair, action must be taken immediately. The only feasible solution is to cut, carefully break, or pull the hair out. If the situation is allowed to continue, your scalp will be pulled into the descender, producing a painful bald spot. If an ascender is at hand, you may be able to attach it and move upward far enough to untangle yourself by releasing weight on the descender. Using hair ties or tucking the hair up under the helmet are highly recommended precautions.
Many experienced cavers recommend gloves to avoid rope burns and abrasion. There is some basis for the wearing of gloves on the braking hand; however, especially on shorter drops, if you need gloves to avoid rope burns from abrasion, you are probably exceeding a safe descent rate. Personal preferences will decide this issue,however, simply wearing gloves does not mean you are able to travel any faster.
Heat is produced through friction during a caver’s descent. It is important to monitor the heating of descending devices, as they have the ability to become hot enough to melt through a rope. If the descender is exceptionally hot, it is also important not to stop and remain in one exact spot, as this permits the hot bar or area on the descending device to affect a very small section of the rope. This may appreciably weaken or damage the rope.
Just In Case
It is a very wise idea to carry your vertical ascending gear with you on any substantial drop of 50 feet or more. If you find that your rope does not reach bottom, you merely switch over to ascending gear and ascend back to the top. When switching over to ascending from descending, you must suspend your weight from the main rope above the descender (through the use of an ascender attached to the main rope) in order to un-weight the descender and disengage it.
Crossing A Knot
It is not uncommon in deep pits and technically rigged caves that the need arises to cross over a knot in the rope while on a rappel. The principle is the same as switching from descending to ascending. In order to descend past a knot, the caver must stop above the knot by about a body length, and attach his ascenders. (If you are going to pass over a knot, you should already know this, and it would be prudent to have already donned your ascending system.) At least one ascender must be attached to the main rope above the descender to allow disengagement of the descender after un-weighting. Once you have attached your ascenders and detached your descender, you simply prusik downward, passing the knot by detaching and reattaching each ascender below the knot, one by one. Once below the knot you re-engage your descender, place your weight on the locked up descender, remove your ascenders, and continue on down.
In learning to rappel, it is psychologically reinforcing to have the rappeller belayed through the use of a separate rope. However, it has been found that the belay rope often causes problems with entanglement and dislodging rocks ,these are often considered to present greater danger to the rappeller than does lack of belay with a separate rope. Therefore, in the modern use of SRT the belay systems using an additional rope are generally not used, except in special circumstances. Obviously this means that any failure in the primary system will possibly result in catastrophic results. Therefore, the primary system must be of fail-safe design.
While a separate belay system is not generally used, the descending caver should be belayed from below whenever possible. This bottom belay is quite effective (provided, of course, that there is no equipment malfunction). The belayer holds the bottom of the rappeller’s rope and monitors the caver’s descent. If the caver yells, “Falling,” or the belayer sees the caver out of control, he needs merely to add tension to the rope. The belayer is essentially doing the same job that the caver’s braking hand does,however, the belayer can increase tension to a greater degree than can the rappeller.
Increased tension on the rope creates increased friction, hence the descending caver comes to a stop. The belayer can actually control the descent of an unconscious caver all the way to the cave floor quite effectively. Remember that on longer drops the belayer must take up rope stretch before tension can be achieved. It is extremely important that the belayer be clear of the rock-wall area below the descending caver.
It is generally a more accepted procedure for the descending caver to use a self-belay. To do this, the caver attaches some type of ascender or prusik knot above his rappel device, holding it in the disengaged mode,if control is lost, he merely needs to engage it by letting go, and the ascender will bring the caver to a halt. In recent years the effectiveness of this system has been questioned. It is often a natural instinct to hold on even tighter to this self-belay device, since it is your balance hand. When gripped, it will not engage. The most effective self-belay device is a modified Gibbs ascender called a spelean shunt. A quick release Gibbs is used with a locking carabiner passed through the eye and around the housing. A piece of webbing is tied from the eye to the chest harness. If control is lost the caver merely leans back, engaging the Gibbs. The carabiner provides a handle to release the activated Gibbs. The chest harness should be attached to the seat harness for safety.
Reaching The Bottom
When descending into a pit and reaching the bottom, be careful that as you get off the rope it does not spring upward out of reach. If the rope is not sufficiently long, it may spring out of the caver’s reach when body weight is removed, due to the stretching characteristics of nylon ropes. This is embarrassing at best, and could present a serious problem.
Instruction & Practice
It is important that the novice caver seek instruction in the equipment and techniques of caving. Every caver should know his equipment implicitly. He should be able to work with his equipment blindfolded, as at some point the caver may well find himself in the situation where he has no light and must finish a descent or ascent in the dark. Underground is no place to learn to use a new piece of equipment. Practice with your equipment outside on open rock and drops. Do not go underground until you are thoroughly familiar with any new equipment and new caving techniques you intend to use there.